Transistor ignition system



Jan. 9, 1968 G. M. FORD TRANSISTOR IGNITION SYSTEM Filed March 29, 1965 INVENTOR. GERALD M. FORD BY 0 IQ: W

ATTORNEY United States Patent 3,363,142 TRANSISTOR IGNITION SYSTEM Gerald M. Ford, Santa Monica, Calif., assignor to General Motors Corp., Detroit, Mich, a corporation of Delaware Filed Mar. 29, 1965, Ser. N 443,218 7 Claims. (Cl. 315269) This invention relates to a transistor ignition system where a transistor controls current flow through the primary winding of an ignition coil in synchronism with the operation of the engine and where the transistor is of the ring emitter type.

It is known in the art of internal combustion engine ignition systems to provide a transistor that is connected with the primary winding of an ignition coil to control current flow in the primary winding. The present invention is concerned with an improved type of ignition system where it is possible to eliminate some of the components which are considered to be necessary for proper operation of a transistor ignition system. Thus it is contemplated by this invention to provide a transistor ignition system which does not require a Zener diode connected across the emitter and collector electrodes of the transistor for protecting the transistor against transient voltage surges and does not require a base resistor that normally connects the emitter and base electrodes of the transistor.

I have discovered that by using a ring emitter transistor which has its center base connection connected to the emitter ring rather than to the base ring, it is possible to eliminate components such as the above-mentioned Zener diode since by this connection of the transistor, the transistor is capable of withstanding the transient voltage surges encountered in an ignition system.

It accordingly is one of the objects of this invention to provide a transistor ignition system that utilizes a ring emitter transistor that has its center base and its emitter ring connected.

Another object of this invention is to provide a transistor ignition system which does not require many auxiliary components such as a Zener diode or a base resistor for proper operation.

Still another object of this invention is to provide a transistor ignition system which has improved temperature compensation characteristics as compared to known transistor ignition systems and wherein the thermal capacity of the transistor is not greatly attenuated.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic circuit of an ignition system made in accordance with this invention.

FIGURE 2 is a diagrammatic illustration of a ring emitter transistor illustrating the connection between the center base and the emitter ring of the transistor.

Referring now to the drawings and more particularly to FIGURE 1, the reference numeral 10 designates a source of direct current such as the storage battery or a generator on a motor vehicle. One side of the source of direct current 10 is grounded while the opposite side is connected with the conductor 12. An ignition switch 14 is provided for controlling energization of the ignition system and the fixed contact of this switch is connected in series with a resistor 16 that feeds a conductor 18.

The ignition system includes an ignition coil generally designated by reference numeral 20. This ignition coil has a primary winding 22 and a high voltage secondary winding 24 which are connected together at junction 26.

3,363,142 Patented Jan. 9, 1968 The ignition system as shown in FIGURE 1 includes a conventional distributor having breaker contacts 28 which are opened and closed in synchronism with operation of the engine. The breaker contacts 28 can be opened and closed by a distributor cam driven by a distributor shaft. This distributor has a distributor cap 30 that carries a plurality of circumferentially spaced electrodes 32 and a center electrode 34. The center electrode 34 is connected with the secondary winding 24 :by a conductor 36. A rotor contact 38 which is driven by the shaft of the distributor and which is synchronized with the opening and closing of breaker contacts 28 serves as a means for electrically connecting the center electrode 34 with the circumferentially spaced electrodes 32. The circumferentially spaced electrodes 32 are connected respectively with the spark plugs of the engine, one of which is illustrated and designated by reference numeral 40. It will be understood that there will be as many electrodes 32 as there are spark plugs as is well known to those skilled in the art.

The transistor of the ignition system shown in FIGURE 1 is generally designated by reference numeral 42. This transistor is of the ring emitter type and has an emitter 44, a first base 46, a second base 48, and a collector 49. The internal construction of a ring emitter transistor is shown in the patent to Baird, 3,089,067. The ring emitter transistor shown in Baird is modified in accordance with this invention in a manner shown diagrammatically in FIGURE 2. Thus in FIGURE 2, the emitter ring is designated by reference numeral 44 while the base 48 takes the form of a base ring. This ring emitter type of transistor has another center base 46 and in the conventional type of ring emitter transistor, the bases 46 and 48 shown in FIGURE 2 are connected by a conductor as is illustrated in the above-mentioned Baird patent.

In accordance with this invention, however, the center base 46 rather than being connected to the base ring 48 is connected to the emitter ring 44 by a conductor 50'. This conductor 50 is shown in FIGURE 2 and in the schematic circuit diagram of FIGURE 1.

'It can be seen from FIGURE 1- that the base ring 48 is connected to one side of the breaker contacts by a conductor 52. The opposite side of the breaker contacts are grounded. The center base 46 is connected with the emitter 44 by the conductor 50. The junction 54 which is connected with the emitter ring 44 and with the center base 46 is connected toone side of the primary Winding 22 of the ignition coil by a conductor 56.

The collector 49 of the transistor is connected to ground as is shown in FIGURE 1.

The operation of the ignition system shown in FIGURE 1 will now be described. When the breaker contacts 28 are closed, base current will flow in transistor 42 from the positive side of battery 10, through conductor 12, through closed switch 14, through resistor 16, through conductor 18, through primary winding 22, through conductor 56, through the emitter-base junction of transistor 42, through conductor 52 and then through the breaker contact 28 to ground. With the transistor 42 biased to a conductive condition as just set forth, the transistor turns on in its emitter-collector circuit which effectively connects the primary winding 22 of the ignition coil across the source of direct current 10. As a result of this, current flows through the primary winding of the ignition coil 22.

When the breaker contacts 28 open, the base circuit for transistor 42 is opened which in effect, opens the emittercollector circuit of transistor 42. When this happens, current flow through the primary winding 22 is cut oif and a large voltage is induced in the secondary winding 24. This voltage is applied to one of the spark plugs 40 via conductor 36, through rotor contact 38 and one of the distributor cap electrodes 32.

It has been found that by connecting the center base of the transistor to the emitter ring, as shown in FIGURES 1 and 2, the transistor ignition system does not require a Zener diode that is normally connected across its emitter and collector electrodes to provide protection against transient voltage surges. In other words, by using the connection 50, the transistor is capable of withstanding voltage surges that may be developed during the operation of the ignition system. In addition, no base resistor which normally connects the emitter and base electrodes of the transistor is required and no diode which sometimes is connected in series with the emitter is required to backbias the transistor. It therefore is seen that the transistor ignition system of this invention eliminates a number of components which have been thought to be required for proper operation of this ignition system. In addition, by using the connection 50, improved thermal stability without greatly diminishing current gain is achieved.

The connection 50 for the transistor can be made by opening a conventional transistor such as a 2N173 transistor and disconnecting the center base 46 from the base ring 48 and connecting this base ring to the emitter ring as shown in FIGURE 2. In transistors where two base electrodes are available, the connection 50 can be made by simply connecting the external base leads.

Although breaker contacts 28 have been disclosed for controlling the switching of transistor 42, it is to be understood that other switching devices can be used such as a switching transistor which is controlled, for example, by a magnetic pick-up driven in synchronism with the engine.

While the embodiments of the present invention as herein disclosed constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A transistor ignition system for an internal combustion engine comprising, a source of direct current, a transistor having emitter and collector electrodes, said transistor including an emitter ring, a center base connection and a base ring, means electrically connecting said emitter ring to said center base connection, an ignition transformer having a primary winding and a secondary winding, means electrically connecting said primary winding and the emitter-collector circuit of said transistor in series across said source of direct current, and means connected with the base ring of said transistor for controlling the conduction of said transistor in synchronism with operation of said engine.

2. A transistor ignition system for an internal combustion engine comprising, a transistor having an emitterring, a base ring and a second base connection, conductor means electrically connecting said emitter ring and said second base connection, a source of direct current, an

ignition coil having a primary winding and a secondary winding, means connecting the emitter-collector circuit of said transistor and said primary winding in series across said source of direct current, and switching means connected with said base ring of said transistor for controlling conduction of said transistor in synchronism with operation of said engine.

3. A transistor ignition system comprising, a source of direct current, an ignition transformer having a primary winding and a secondary winding, a transistor having a ring shaped emitter, a ring-shaped base and a second base connection, means connecting said ring-shaped emitter and said second base, means connecting said primary winding between one side of said source of direct current and said ring-shaped emitter, means connecting the collector of said transistor to an opposite side of said source of direct current and a switching means operated in synchronism with said engine connected between said base ring and one side of said source of direct current.

4. The ignition system according to claim 3 where the switching means are the breaker contacts of a distributor.

5. A transistor ignition system comprising, a transistor, said transistor having an outer base ring, an emitter ring located within said base ring and a base connection located within said emitter-ring, conductor means electrically conmeeting said base connection and said emitter ring, a source of direct current, an ignition coil having a primary winding and a secondary winding, means connecting the emitter-collector circuit of said transistor and said primary winding in series across said source of direct current, and means operated in synchronism with said engine and connected with said base ring for controlling the conduction of said transistor in its emitter-collector circuit in synchronism with operation of said engine.

6. The ignition system according to claim 5 where the means for controlling the conduction of the transistor is a switching means operated in synchronism with the engine.

7. The ignition system according to claim 5 where the means for controlling the conduction of the transistor comprises distributor breaker contacts connected between said base ring and one side of said source of direct current. 7

References Cited UNITED STATES PATENTS 9/1958 Johnson 315209 1/1963 Short 315209 

1. A TRANSISTOR IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING, A SOURCE OF DIRECT CURRENT, A TRANSISTOR HAVING EMITTER AND COLLECTOR ELECTRODES, SAID TRANSISTOR INCLUDING AN EMITTER RING, A CENTER BASE CONNECTION AND A BASE RING, MEANS ELECTRICALLY CONNECTING SAID EMITTER RING TO SAID CENTER BASE CONNECTION, AN IGNITION TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANS ELECTRICALLY CONNECTING SAID PRIMARY WINDING AND THE EMITTER-COLLECTOR CIRCUIT OF SAID TRANSISTOR IN SERIES ACROSS SAID SOURCE OF DIRECT CURRENT, AND MEANS CONNECTED WITH THE BASE RING OF SAID TRANSISTOR FOR CONTROLLING THE CONDUCTION OF SAID TRANSISTOR IN SYNCHRONISM WITH OPERATION OF SAID ENGINE. 